To reduce air pollution, engine exhaust emissions standards have become increasingly more stringent. After treatment devices have been developed to satisfy these increasingly stringent standards. For example, catalytic converters have been used to reduce the concentration of pollutant gases (e.g., hydrocarbons, carbon monoxide, nitric oxide, etc.) exhausted by engines. With respect to diesel engines, diesel particulate filters have been used to reduce the concentration of particulate matter (e.g., soot) in the exhaust stream. U.S. Pat. No. 4,851,015, which is hereby incorporated by reference, discloses an example diesel particulate filter. Other example types of after treatment devices include lean NOx catalyst devices, selective catalytic reduction (SCR) catalyst devices, lean NOx traps, or other device for removing for removing pollutants from engine exhaust streams.
At times, it is required to service after treatment devices. To facilitate servicing, after treatment devices are often clamped into an exhaust system as modules or separate units. For example, clamps can be provided at flange interfaces located opposite adjacent opposite ends of the after treatment devices. By removing the end clamps, a given after treatment device can be removed from its corresponding exhaust system for servicing.
In use, after treatment devices occasionally become overloaded with soot, ash or other materials present in or generated from engine exhaust. As after treatment devices become overloaded, the devices cause undesirable backpressure in their corresponding exhaust systems. Before an after treatment device becomes plugged to the point where excessive backpressure is a concern, it is recommended to remove the device from its corresponding exhaust system for servicing. To service a device such as a diesel particulate filter, it is known to manually move a focused stream of pressurized air back and forth across the outlet side of the filter to loosen soot/ash that has collected on the filter. For example, a dry air gun (e.g., 50-100 psi) can be used as a source of pressurized air. Simultaneously, an industrial vacuum device is coupled to the inlet side of the filter. The vacuum device is typically equipped with a high-efficiency particulate air filter or ultra-low penetration air filter for collecting the soot/ash that is blown from the filter by the pressurized air. Total time for cleaning the filter depends on the size of the filter, but is typically 30-50 minutes.
Pulse cleaners have been used in other filtration applications to clean filters. For example, industrial dust collection systems have been designed with “self-cleaning” filters for removing dust from an air stream (e.g., see U.S. Pat. No. 4,159,197). These systems have filters (e.g., pleated filters or bag filters) that are cleaned inset (i.e., on-line). For example, while the systems are in use collecting dust, the systems periodically use nozzles to direct pulses of air at the filters in a reverse-flow direction (i.e., in a direction opposite to the flow of air being filtered) to drive or shake collected dust from the filters.
What is needed is an improved device/method for servicing overloaded diesel particulate filters or other exhaust after treatment devices.